Net-zero Energy Buildings Becoming More Common

Skeptics may scream "science fiction," but the idea of buildings producing as much energy as they use each year is an idea whose time is nearing. In fact, experts say, net-zero energy buildings is the next big movement in green design.

Major players in the industry — including the Department of Energy, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the American Institute of Architects — have rallied around the idea and are taking concrete steps to turn the seemingly farfetched concept into reality. Their goal is to make net-zero energy the standard for building design and operation over the next 20 years.

A lot has to happen over the next two decades for that vision to come to fruition. But important activity is already underway. And a variety of forces are likely to accelerate the move to net-zero energy buildings.

Net-zero energy buildings are truly the next stage of environmentally responsible building. They are the embodiment of sustainability because net-zero energy is a model that is self-contained — no outside resources are required and the model can therefore be sustained ad infinitum.

The appeal of that simple idea is likely to grow more powerful as sustainable design continues to penetrate the mainstream of design and construction practices.

Today, green buildings, especially LEED-certified ones, are still viewed by many as cutting edge. But the more green buildings there are, the more owners and developers will look for ways to distinguish their green buildings from the growing mass of other green buildings. A net-zero energy approach will be a powerful method of market differentiation.

The impetus behind net-zero energy goes beyond market forces. A net-zero energy approach is an essential element of any strategy to address climate change. Legislation like the Waxman-Markey bill, which passed the House last summer and is awaiting vote in the Senate, could put a real, tangible dollar amount on emissions, so reducing emissions preemptively can certainly pay dividends later.

Indeed, concerns about climate change have given the move to net-zero energy an industrywide urgency. The Department of Energy's Net-Zero Energy Commercial Building Initiative, armed with millions of stimulus dollars, has pledged to make commercial net-zero energy buildings marketable by 2025. Providing tools, like Advanced Design Guidelines, and case studies of existing net-zero energy buildings, the Initiative will also fund research in lighting, indoor environmental quality, building controls and diagnostics, and space conditioning.

ASHRAE's Vision 2020 pledges to make the tools necessary to design, build and operate net-zero energy buildings available by 2020 so that they're actually market-viable by 2030. As part of this goal, ASHRAE will continuously update its hallmark 90.1 energy standard to make it much more stringent over the next two decades. The organization envisions that net-zero energy buildings will eventually be standard practice.

And the well-known Architecture 2030 Challenge sets a stepped timeline for designers and owners to make net-zero energy buildings standard operating procedure by 2030.

Taken together, those initiatives make it clear that the net-zero energy approach is hardly a pipe dream. But right now only a handful of buildings meet the net-zero criteria. And most of them are small, ultra-efficient one- or two-story buildings that use on-site renewable energy technologies, like photovoltaic panels, to produce an annual total of 100 percent of the electricity that the buildings require.

The Adam Joseph Lewis Center for Environmental Studies at Oberlin College is one such example. The two-story, 13,600-square-foot building produces all its energy on-site with two different PV arrays — a 60 kW on the roof and a 100 kW located over the parking lot.

Work is now underway to try to make that approach work for larger buildings. For example, the Department of Energy's Research Support Facility on the National Renewable Energy Laboratory (NREL) campus in Golden, Colo., is a 219,000-square-foot facility that is expected to be the largest truly net-zero energy facility in the United States. Intended to be a showpiece for what is possible, the building is scheduled to open in the summer of 2010.

But the NREL and Oberlin buildings are still very much exceptions to the rule, not models that facility managers can copy. In fact, before net-zero energy buildings become widespread, there is likely to be a period of time when facility managers aiming for that goal will have to rely on a three legged stool: energy-efficiency, on-site renewable energy, and the purchase of renewable energy from the grid.

"The best solution is producing all energy on-site," says Dru Crawley, team leader, commercial building research and development for the Department of Energy's Building Technology Program. "But we realize that most net-zero energy buildings will cascade down to using renewable energy certificates or other green energy purchases to close the gap."

Carbon Neutral vs. Net-zero Energy

The terms "carbon neutral" and "net-zero energy," as they're applied to buildings, are often used interchangeably. In most cases, this is a mistake, say experts. The terms are not synonymous — though, in some cases, they can both apply to a building.

A truly net-zero energy building is one that generates 100 percent of its power from renewable sources on-site all the time. That means it is completely grid-independent and therefore is never using any fossil-fuel-generated energy from a power plant. This type of net-zero energy building is also carbon neutral because no carbon dioxide emissions are released to the atmosphere.

However, because a net-zero energy building is defined as one that produces at least as much energy as it uses on an annual basis, there are times — peak demand times, for instance — when even the best net-zero energy buildings may be drawing from the grid. As soon as they draw a single electron from the grid, they cease to be carbon neutral, even if they make up that energy later in low-demand times with a surplus of renewable energy.

"Any project that draws on the grid is using fossil fuel-supplied energy," says Brad Jacobson, project manager and associate with EHDD Architecture. "So that means the project is not carbon neutral. Carbon neutrality is a different and more difficult goal than net-zero energy."